|The origin of CO in Uranus
|One of the Infrared Space Observatory.s most important results is the detection of H2O and CO2 in the giant planet stratospheres. The presence of a condensible species (H2O) above the tropospheric cold trap implies an external origin of H2O. This oxygen supply, which manifests itself also through the presence of CO2 and CO in these atmospheres, may have several sources: a permanent flux from interplanetary dust particles, local sources (rings, satellites), or large comet impacts. However, observing CO in the stratospheres of the giant planets does not automatically imply only an external origin of this species because there is no condensation sink at the tropopause for CO. Thus, it can be transported from the deep hot interior of the planet to the stratosphere. CO can have either an internal origin, an external origin or a combination of both. Spectrally-resolved, high signal-to-noise ratio and spatially-resolved (when possible) observations are needed to disentangle the various sources. While Jupiter, Saturn and Neptune have all an external source of CO, probably of cometary origin, and an internal source (not yet demonstrated but likely in Saturn), the situation remains unclear at Uranus despite the detection of CO from its 5 micron fluorescence. So far, we have not detected CO from the ground in the (sub)millimeter range but we obtained a tentative detection of the CO(8-7) line with HIFI in July 2011 in the framework of the HssO Key Programme. Because external sources of CO seem to be active for all the other giant planets, we propose to observe Uranus at the frequency of the CO(8-7) line with HIFI in order to confirm our tentative detection in the submillimeter range. We will obtain a spectrally-resolved and high signal-to-noise ratio observation of the lineshape that will enable us to retrieve information on its vertical distribution. Thus, we will be able to discuss the origin of CO in Uranus from this observation.
|The first submillimeter observation of CO in the stratosphere of Uranus . Cavalié T. et al. . Astronomy & Astrophysics, Volume 562, id.A33, 6 pp. . 562 . 10.1051/0004-6361/201322297 . 2014A&A...562A..33C ,
|Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
|Publisher And Registrant
|European Space Agency
|European Space Agency, 2012, OT2_tcavalie_6, SPG v14.1.0. https://doi.org/10.5270/esa-u6mwjfi